Truck and bus suspensions utilize at least one torque rod assembly to secure the drive axle to the vehicle's frame. The securing of the drive axle to the vehicle's frame by the torque rod assembly maintains the drive axle's alignment to the vehicle's frame, it maintains the proper suspension geometry for the vehicle, and it allows fore suspension movement in both jounce and rebound for all terrain, road and driving conditions. Because of the wide range of dynamic operating conditions for these vehicles, especially heavy duty trucks, the severe impact loads to the suspension system combined with the road induced vibrations on the suspension system lead to deleterious effect on the individual suspension components including the torque rod assemblies as well as having a negative impact on the operator's physical fatigue condition. These severe dynamic conditions can accelerate wear of the torque rod assemblies of the suspension system leading to premature deterioration of these torque rod assemblies.
As described above, the purpose of torque rod assemblies on large vehicles is to stabilize the axle. They prevent the axle from rotating about its own axis, they prevent the axle from moving fore and aft during braking and acceleration, and they prevent axle yaw. While there are a variety of suspension designs, one of two approaches are generally used to stabilize the axle. The first approach uses straight torque rod assemblies which have a center torque rod and pivotal joints at either end. Two of these straight rods are typically mounted fore and aft on the vehicle, where one end is mounted to the axle and the other end is mounted to the frame. An additional straight torque rod assembly is similarly mounted laterally in the vehicle, generally perpendicular to other torque rod assemblies. The second approach is to incorporate a V-configuration torque rod assembly. This type of torque rod assembly has pivotal joints at the apex of the V as well as at the end of each leg. The apex is typically mounted to the axle and the legs are then mounted to the frame. The V-configuration torque rod assemblies control both fore and aft movement as well as lateral movement. The major advantage to the V-configuration torque rod assembly is axle stability.
A typical prior art straight torque rod assembly or V-configuration torque rod assembly is comprised of two or three pivotal joint eyelet forgings rigidly connected to each other with a center torque rod to provide mechanical integrity. The center torque rod can be a solid or tubular rod. The eyelets and the center rod form a natural path for shock and vibration energy to transfer from the suspension system into the frame, the cab and other areas of the sprung mass of the vehicle. In order to isolate this path, an isolation function has been incorporated into a pivotal joint assembly mated with each eyelet. This isolation function thus makes the pivotal joint assembly a critical multi-functional component for the torque rod assembly as well as the suspension system as a whole.
Due to tolerance stack ups and other variations encountered during the assembly of the vehicle, it is sometimes desirable to provide adjustability to the center torque rod of the torque rod assembly. A typical prior art adjustable torque rod assembly 200 is illustrated in FIG. 6.
Torque rod assembly 200 comprises a pair of pivotal joint assemblies 202, a solid rod 204, a solid rod 206 and an attachment clamp 208. Each solid rod 204 and 206 include an enlarged section 210 which is headed on the ends of rods 204 and 206 and enlarged section 210 is welded to a respective eyelet 212 of pivotal joint assembly 202.
Attachment clamp 208 comprises a tubular housing 222 having a pair of radially extending ears 224. Solid rod 204 defines a threaded end 226 and solid rod 206 defines a threaded end 228. Tubular housing 222 defines a threaded bore 230 into which threaded end 226 of solid rod 204 and threaded end 228 of solid rod 206 are assembled. Once the appropriate engagement length between threaded end 226 and bore 230, the appropriate engagement length between threaded end 228 and bore 230 and thus the appropriate length of torque rod assembly 200 is set, a pair of bolts 232 are inserted through ears 224 and a pair of nuts 234 are threaded onto bolts 232. Nuts 234 are tightened to secure the attachment of clamp 208.
While the above described design for an adjustable length torque rod assembly has performed satisfactorily in the various suspensions, there are several issues that need to be addressed with regards to this design. First, the number of components that are needed for this design are excessive. This leads to excessive costs, inventory problems and logistics problems throughout the manufacturing process. Second, the assembly of the above design design is labor intensive which leads to excessive costs during the assembly of the system.